1. Field of the Invention
The present invention relates to a machine tool, and particularly relates to a machine tool provided with a door opening/closing device that can achieve safety at low cost.
2. Description of the Related Art
In a machine tool, a machining area is covered by a fixed cover typically called a splash guard to protect an operator from scattered pieces coming from coolant used in fabrication, chips generated in fabrication, cutter and tooling used in fabrication, a workpiece or the like. A movable door is provided in part of the fixed cover so as to allow the operator to perform replacement of workpieces, and maintenance work such as cleaning of inside of the machine and routine inspection.
The movable door may be a manual door, which is opened and closed by the operator, or may be an automatic door using a servomotor or an air cylinder to achieve a shorter door opening/closing time and automation using a robot (refer to Japanese Patent Laid-open No. 2006-075916, for example).
The automatic door opening/closing has a potential risk that the operator or the robot may be caught in the door due to an unexpected accident such as a false operation by the operator, which may result in injury or damage. In order to prevent such a situation, a sensor (area sensor) configured to detect existence of a human or an object in the machine is typically used. However, such a sensor is likely to be expensive, causing a cost problem.